The development of interactive graphics computer systems for use in the detection, Identification, and transformation of patterns contained in high-dimensional data has been a continuing program at the Rome Air Development Center since 1968. This long standing effort has resulted in the implementation of OLPARS (the On-line Pattern Analysis and Recognition System), IFFS (the Image Feature Extraction System), and WPS (the Waveform Processing System). This report contains detailed design and user-oriented information related to MOOS (the Multics OLPARS Operating System), an advanced version of OLPARS currently resident upon the Honeywell 6180 MULTICS computer system. The currently operational system represents an implemented version of the operations described in a previous report (RADC-TR-73-241); appropriate selections of that report are retained within this document. This report contains brief descriptions of the MOOS system and the mathematics underlying the system algorithms. A major portion of this document is reserved for a user's manual (providing detailed information relating to the operation of all system options) and for MOOS program documentation.